The Events option when right-clicking on a button control gives you a list of scripts attached to that button.
You can add a new script with the 
icon, or attach an existing script from the workspace with the 
icon.
When the button is clicked, all the attahced scripts are triggered in the order they are listed, from top to bottom.
You can remove a selected script with the 
icon. This only removes the script from the button, and does not delete it from the workspace.